About 85% of salivary gland tumours occur in the parotid gland (A, and B, Fig. 32-10), 10% in the submandibular gland, and 5% in the mucous secreting glands inside the mouth, especially on the palate (C, Fig. 32-9). Similar tumours occasionally arise from the lachrymal gland (24.10).
There are several histological varieties:
The relatively benign ones are: (1) pleomorphic adenomas, (2) monomorphic adenomas, (3) and adenolymphomas (usually cystic).
The more malignant ones are: (4) adenocarcinoma (including cylindroma), (5) muco-epidermoid carcinoma, (6) pleomorphic adenocarcinoma, and (7) squamous cell carcinomas. Malignant tumours need radical excision, but even after this, some recur locally. Spread to the lymphatics and bloodstream is usually late. In Caucasians, 80% of salivary gland tumours are fairly benign pleomorphic adenomas, which may infiltrate the ''capsule' of the gland, but do not metastasize. In Africans, only 50% of tumours are of this kind.
The patient presents with a slowly growing mass in one of his salivary glands, usually his parotid, but occasionally at an ''ectopic' site inside his mouth, particularly in his hard palate. If he has any sign of a facial palsy, his facial nerve is involved, and his tumour is malignant. Unfortunately, the absence of a facial palsy does not mean that his tumour is benign.
SALIVARY GLAND TUMOURS THE DIFFERENTIAL DIAGNOSIS includes: (1) Leukaemic deposits in a patient's salivary glands (examine his blood). (2) Enlarged lymph nodes in his parotid gland, from either non- specific infection, or tuberculosis (unusual). (3) Hypertrophy of the gland, due to obstruction by a stone.
CAUTION ! Don't biopsy the growth. This may spread a pleomorphic adenoma locally, and you may damage his facial nerve.
MANAGEMENT. Facial palsy is the critical sign.
If he does not have a facial palsy his growth should be excised completely, and not merely shelled out. This makes sure that the commonest lesion (a pleomorphic adenoma) is completely removed, and will not recur. He needs a conservative parotidectomy, in which the fine branches of his facial nerve are dissected out, and the part of the gland containing the growth removed; either its superficial part, its deep part, or both.
If he has a facial palsy, his prognosis is poor, even after radical surgery and radiotherapy.
Both conservative parotidectomy and radical resection are difficult[md]refer him to an expert. This is important, because the correct surgery will cure a pleomorphic adenoma, if it is early.